Parkinson's disease (PD) is a slowly progressing, degenerative condition. It's the most common form of parkinsonism, a group of motor system disorders. The specific cause of PD is unknown. But medical experts believe the symptoms are related to a chemical imbalance in the brain caused by brain-cell death. The symptoms of PD, which grow worse over time, result from the loss of dopamine-producing brain cells. Dopamine is a substance produced in the body that has many important effects, including smooth and coordinated muscle movement. The biggest risk factor for developing PD is advancing age. The average age for the onset of PD is 60. In addition, 50% more men are affected than women. However, the reason for this is unclear. Family history is another important risk factor. Individuals with a parent or sibling who are affected have approximately two times the chance of developing PD. This increased risk is most likely because of a combination of environmental and genetic factors. Environmental causes are being researched. The strong consistent findings are that rural living, exposure to well water, and exposure to agricultural pesticides and herbicides are related to PD. It is important to remember, however, that these factors do not guarantee the development of PD. At the same time, their absence does not prevent it. The symptoms of PD may appear slowly and in no particular order. Early symptoms may be subtle and may progress over many years before interfering with normal daily activities. As the disease progresses, walking may become affected. The person may stop in mid-stride or "freeze" in place, and maybe even fall over. People with PD may also begin walking with a series of quick, small steps as if hurrying forward to keep balance, a practice known as festination. Accurately diagnosing PD in the early stages can be difficult. The beginning signs and symptoms of the disease may be similar to other conditions and can mimic the effects of normal aging. Currently, there are no laboratory tests used to diagnose PD. Diagnosis is based primarily on a medical history and thorough neurological examination. Brain scans and/or lab tests may be performed to help rule out other diseases or conditions, but a brain scan generally will turn out to be normal with PD. Other methods of diagnosis may include the following: Trial test of drugs (primarily levodopa)—if a person fails to benefit from levodopa, a diagnosis of PD may be questionable Computed tomography scan Magnetic resonance imaging Despite highly focused, aggressive research, we have yet to find a cure for PD. However, based upon the severity of the symptoms and an individual's medical profile, treatment for PD may include medications, surgery, and complementary and supportive therapies, such as diet, exercise, physical therapy, occupational therapy, and speech therapy. Most treatments are aimed at helping the tremor or rigidity that comes with the disease. In some patients, surgery may decrease the amount of medication that is needed to control symptoms. Surgery may help with symptoms of PD, but it does not cure the disease or stop the progression of the disease.